See thousands of orchid plants in bloom (October is peak season), get expert advice, listen to lectures and peruse a sales tent full of quality plants and supplies at the National Arboretum’s Annual Orchid Show and Sale from 9 a.m. to 5 p.m. Sunday. Next Saturday, the arboretum will sell most of its popular koi from 9 a.m. to 2 p.m., with a preview starting at 8 a.m. The colorful fish, which range from $1 to $150, depending on size and quality, must be sold because their pool is being drained for renovations. All sales are final. 3501 New York Ave. NE. 202-245-2726. www.usna.usda.gov

Through Monday, during Potomac Mills’s Fall Super Sale Weekend, save more on already-discounted apparel, accessories, home goods and electronics at more than 200 off-price stores, including Last Call by Neiman Marcus, where you can take an additional 30 percent off your entire purchase. 10 a.m.-9 p.m. Monday-Saturday, 11 a.m.-6 p.m. Sunday. 2700 Potomac Mills Cir., Woodbridge. 703-496-9330. www.potomacmills. com.